[MW:23629] RE: 23626] Re: NEED ADVISE CORROSION IN INHIBITOR TANK REGD

From this I understand that it is a 316L vessel which is exposed in an offshore marine environment and has a nominal operating temperature of up to 40 degrees C and after 5 years exposure is showing signs of external pitting corrosion. I believe the reason why this has occurred is straightforward; it is operating at a temperature and in an environment where pitting is inevitable. The critical pitting temperature of 31L stainless steel is about 15 degrees C in a chloride bearing environment for solution treated 316L. Although 316L is used in marine environments it performs without pitting only at moderate temperatures [and even at moderate temperatures it will show signs of corrosion in crevices] . I also suspect the steel temperature may be higher than the greatest ambient/operating temperature of 40 deg C due to solar gain, which makes the situation worse. Alongside the welds you may be suffering crevice corrosion. Iron contamination could also be a factor particularly with some of those surface lines away from welds due to contact with carbon steel materials.

 

In my view it comes down to understanding the environment in which the material is to be exposed, (marine and high temperature relative to CPT) and the limitations of 316 stainless steel. There is a lot of information on the web if you do a search. The material selection is hence wrong for the external environment, or the tank should have been painted – yes you do paint stainless steel!

 

Alan Denney

AKD Materials Consulting Ltd

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com]
Sent: 30 September 2015 10:55
To: pgoswami <pgoswami@quickclic.net>
Cc: <materials-welding@googlegroups.com> <materials-welding@googlegroups.com>
Subject: [MW:23626] Re: NEED ADVISE CORROSION IN INHIBITOR TANK REGD

 

Dear Sir,

 

It's is a corrosion inhibitor storage tank for subsea pipeline project , 

 

operating temperature is 40degree Celsius ,

Operating pressure.     Is .7KPA

Chemical is injected inside the tank , as per design data sheet there is no insulation.

 

Now I have planned to visit the location and provide more information in environmental condition,

Almost 5years completed and dispatched the job.

P.NEILASHKUMAR 

Sent from my iPad

MOB : 966 533098265

            91+9952110791

On Sep 30, 2015, at 5:27 AM, pgoswami <pgoswami@quickclic.net> wrote:

Hi Neileshkumar,

What're the surrounding operating or environmental conditions around the tank. Are there any acid fumes involved. Looks like this tank was not insulated at all??? Is that true.

Appreciate more information on the operating conditions.

 

Thanks

 
Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Engineering Specialist
Hamilton, Ontario, Canada
pgoswami@quickclic.net
pradip.goswami@gmail.com
ca.linkedin.com/pub/pradip-goswami/5/985/299

-----Original Message-----
From: Neilash Kumar [mailto:neilashkumar@yahoo.com]
Sent: Tuesday, September 29, 2015 2:45 AM
To: Pgosami Sir; Pgosami sir
Subject: NEED ADVISE CORROSION IN INHIBITOR TANK REGD

Dear Sir,

Good Morning, please find the attached tank drawing fabricated by us for our client & it is corroded fully , Can you please clarify,

1. Why the tank are corroded So fast?
2. Can you please advise us the method to stop /reduce the rate of corrosion by applying a top coat &  what type of coating to be applied?

please advise me . Material is 316L tank.

Regards
P.Neilashkumar

<Tank Corrosion.pdf>

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